1. The Field of the Invention
This invention relates to the field of wireless local area networks (LANs). In particular, the invention relates to assigning spectrum to access points in a wireless LAN.
2. A Description of the Related Art
Computer networks supply data and services to the computers and devices connected to the network. Traditionally, the connection to the network has been through a wired medium such as coaxial cable, fiber optics, twisted pair, etc. However, there are a number of applications that benefit from a completely, or partially, mobile computer (or other device). Such computers connect to the network using wireless communications. Wireless communications rely on data transfers using radio transmitters and receivers.
A wireless LAN includes access points and wireless network nodes. The access points connect wireless network nodes to the wired part of the LAN or to some other wireless part of the LAN. An access point communicates, using wireless communications, with the wireless network nodes in that access point's communications area. Thus, an access point maintains a number of simultaneous wireless communications links with a number of wireless network nodes. The access points and the wireless network nodes include transceivers (transmitters and receivers) to establish and maintain the wireless communications links. The transceivers transmit and receive signals in the electromagnetic spectrum, for example, in the infrared spectrum, at 902 MHz or at 2.4 GHz.
The access points typically support multiple channels. This allows two or more access points, communicating on different channels, to have overlapping coverage areas. Different channels can be supported by access points in different ways. For example, Proxim, Inc. supplies a wireless LAN product line called RangeLAN2.TM.. The RangeLAN2 uses frequency hopping spread spectrum communications. A RangeLAN2 transmitter hops from frequency to frequency while transmitting to a receiver. Different channels are supported by different, orthogonal, hopping sequences. Another technique is called direct sequence spread spectrum (DSSS) communications. DSSS breaks the electromagnetic spectrum into a number of sub-bands. Each sub-band corresponds to a different channel.
One of the problems with DSSS communications, or any communications technique where a channel corresponds to a specific part of spectrum, is that access points with overlapping coverage areas need to be assigned to different channels. If access points with overlapping coverage areas are not assigned to different channels, then the transmissions will interfere with each other. This leads to a need to assign different channels to the access points that have overlapping coverage areas.
To adjust for changes in the wireless communications environment, new access points may be added or access points may need to be moved. This may change the overlapping areas of the access points, possibly causing some access points to interfere with other access points. Thus, what is needed is a method and apparatus for displaying the amount of interference between access points and for generating a new set of channel assignments for the access points that will reduce, or eliminate, the interference of the access points.